1. Technical Field
The present invention relates to a light-adjusting unit and a projector.
2. Related Art
In the related art, a projector configured to modulate a light flux emitted from a light source unit by a light-modulating unit according to an image signal and project the modulated light flux on a screen or the like as image light is known. Examples of such a projector include those having a light-adjusting unit configured to adjust the light amount of the light flux to be caused to enter the light-modulating unit corresponding to the brightness of an image to be projected. The projectors having such a light-adjusting unit provide high dynamic contrast.
A light-adjusting unit disclosed in JP-A-2010-175679 includes a dimming unit configured to dim a light flux emitted from a light source, a second gear and a third gear having a dimming unit mounted thereon and configured to rotate for changing the position of the diming unit, a base portion having a supporting shaft configured to rotatably support the second gear and the third gear and configured to sandwich the second gear and the third gear respectively with an optical component housing in the direction substantially orthogonal to an axial center of the supporting shaft. In this configuration, the supporting shaft is allowed to be projected from a rotating portion, the rotating portion is prevented from coming apart from the supporting shaft without arranging a guard ring or the like, and a stable rotation is achieved in order for changing the position of the dimming unit adequately.
In the light-adjusting unit disclosed in JP-A-2010-175679, the second gear and the third gear are provided on the same side as the side where the dimming unit (light-shielding plate) is provided with respect to the base portion. In other words, the second gear and the third gear are provided on the side where the light flux passes, and are subject to a transfer of heat generated by the light flux blocked by the dimming unit. Therefore, there is a problem that the second gear and the third gear expand by the transfer of the heat, and a seizure of these gears with each other (a state of being stuck and immobilized) may often occur. For reference, the second gear and the third gear are formed of synthetic resin or the like having the high heat resistance. In the light-adjusting unit disclosed in JP-A-2010-175679, the second gear and the third gear have a configuration of a spur gear. Therefore, the light-adjusting unit has a problem that a noise is liable to occur due to the engagement between the gears at the time of driving. Therefore, for the purpose of silencing at the time of driving, a method of applying lubricant such as grease is employed. However, problems such as an increase in noise when being used for a long time, seizure of foreign substances adherent to grease between the gears, and unstable operation under a low temperature environment still exist.
Therefore, a light-adjusting unit and a projector capable of inhibiting the thermal transfer to the gears and a reduction of the noise at the time of driving have been demanded.